458 



ANATOMY IX A NUTSHELL. 



Blood Supply. — Intercostal arteries. 



Internal intercostal*. — Description. — These are eleven in number. Their 

 tillers pass obliquely downward and backward in the opposite direction to those 

 of the External intercostals. They extend from the sternum anteriorly to the 

 angles of the ribs posteriorly. 



Origin. — From the inner surface of each rib and the costal cartilage. 



[NSERTION. Into the upper border of the rib below. 



Action. — To depress the ribs and diminish the thoracic cavity. At the 

 from of the chest the Internal intercostal muscles help the External intercostal 

 muscles in raising the cartilages. 



PLATE CCXLVI. 





MASTOID PORTION 



MASSETER. 

 CLASERIAN FISSURE 

 CLENOID FOSSA. 



EXT. AUDITORY MEATUS 

 STYLOID PROCESS - 

 STYLO- GLOSSUS 

 STYLO-HYOID 



^'.W^J^ TRACHELOMAST. 



DIGASTRIC. 

 SPLEVHUS-CAPITIS. 

 STERNOCLEIDOMASTOID- 

 RETRAHENS AURICULAM 



The External Surface of Temporal Bone. 



PROCESS. 



STYLO- PHARYNGEUS. 



Nerve Si pply. — Intercostal nerves. 



Blood Supply.— Intercostal arteries. 



Infracostals, also called Subcostals. — Description. — These muscles vary 

 in their size and number and are placed on the inner surface of the ribs where the 

 Internal intercostals cease. 



Origin. — From the inner surface of the rib. 



Insertion. Into the inner surfaci > of the first, second or third rib below. 

 Their direction is like thai of the Internal intercostals. They are more often 

 presenl between the lower ribs than between the upper ribs. 



Ai i [on. Depress ribs. 



N u;\ i. Si I'i'i.i . Intercostal uerves. 



Blood Supply. Intercostal arteries. 



Triangularis sterni. Des< ription.- This muscle is situated upon the inner 

 wall of the chesl anteriorly and consists of thin muscular and tendinous fibers. 





